Can anyone offer any advice on my engine troubles.

Whenever my engine gets hot I get bubbles of air in the header tank. This is at its worst when I kill the ignition after a run.
I have a 1300 x-flow engine that is cooled by a VW Polo rad.
I can rule out overheating and hence boiling because the fan doesn't kick in and I know that this works reliably at 95degC.
I've also had my head skimmed to rule out leakage past the gasket commonly caused by a warped head.

Anyone got any ideas, I'm starting to loose my patience!!!

I had a similar problem with mine when I first got it running. It was due to an airlock in the cooling system. This prevented correct flow around the system such that, although the radiator was not hot enough for the fan to come on, the water in the head was boiling. This then pumped water out of the header tank and continued to do so for some time after the the engine was switched off.

I'm using a Fiesta thermostat housing, and ran the engine with the (unused) rad stat removed. I then topped up the header tank until water came out of the rad stat hole and then screwed the rad stat back in. Seems to have done the trick.

Worth a try.

Hope this helps.

David

Have you got a by-pass hose fitted ? --- this is a smallish bore pipe that connects the outlets where the heater used to connect it is required to ensure proper flow through the head and block it helps avoid hot spots forming in the head and block due to poor circulation.

It may help to drill a tiny hole in the thermostat valve plate and also you could fit a cooler thermostat but under no circumstances run without a thermostat --- as it is very bad for the engine and xflos have big enough problems with cylinder bore wear.

Also check the ignition isn't set too far retarded as this can cause excessive heat rejection to the coolant at idle speed.




[Edited on 16/8/05 by britishtrident]

Have you got an overflow pipe fitted from the thermostat housing into an expansion tank?
When the water gets hot it expands, and needs somewhere to go(OFlow tank). As it cools, it contracts, sucking water back from the Oflow tank.
Cheers John

Thanks for the advice guys.

JohnJulie my overflow pipe is connected as you say however I get unusually large amounts of air bubbling in the tank, to the extent that it overflows.

I have a bypass pipe fitted where the heater used to be.

I also already have my fan switch running off the fiesta housing rather than the rad.

I had removed the thermostat in a attempt to improve circulation but I think i'd better replace it if it can cause engine damage!

I've considered an airblock and tried filling the engine from the fiesta housing with the temp sender removed, I'll try DavidM's technique when I get a chance.

Fingers crossed

When I filled my x flow system for the first time I removed the thermostat and housing then started to fill the system from the header tank mounted on the bulkhead at the highest part of cooling system . When coolant started to run out off thermostat position in cylinder head I then refitted the thermostat and housing and finished filling system . This method should bleed any air from cooling system especially from below thermostat . I have a heater fitted so coolant flows through inlet manifold and back to water pump. So far I've not had any problems. HTH

When you start up from cold, can you see a lot of movement in the water when the thermostat cap is removed. When I say movement, I mean a lot of bubbling. If yes, you may have an air leak somewhere.
Have you tried re-tightening the head.
From what you describe, it looks like you've still got a seal problem. Could be the head. Has it ever run OK?
Cheers John

I had the exact same symtoms. Bubbled over like a kettle when engine stopped.
It was cured by getting a garden water hose and forcing water from the carb water hose back through the system.
Cured!!!
So it was defo an air buble.

I agree with all of the above!

Some time ago I ran a really long thread on overheating problems with my 1600 x-flow. All sorts of wild theories proposed by well-meaning folk, but the recurring theme was 'airlock'. I even considered swapping from a simple expansion tank to a pressurised header.

In the end, I drained and refilled it a number of times, squeezing hoses etc.; finally it all got sorted and the simple expansion tank now works perfectly.

One thing you could try - drill a small hole (1.0 - 1.5 mm) in the thermostat, near the edge where it won't interfere with the working parts. This allows the air that always gathers under the stat to leak upwards, letting the water fill the entire system.

Good luck, and keep at it!

David

lovely thread, answers most of my problems. My system (xflow) seems to be filled via the radiator, which is just below/almost level with the thermostat. I have decided to plumb in a header tank, as theres lots of space beside the battery, and i feel more familiar with this system. Is it ok to plumb the thermostat to the top of the header tank, and the bottom into a tee in the bottom hose?

Where should the heater bypass run from and to? Should check that that is done right too

New rad should arrive next week, so all smiles soon!

forgot to mention, the start of all this wondering is that the top hose has no water in it at all!

[Edited on 19/8/05 by JoelP]

why not plumb it into the circuit that comes from the carb manifold to water pump? Similar sized tubes then so it should be easier to plumb in

i always assumed that an header tank needed two pipes, like an in and an out. Would certainly make it easier to aviod air locks! Ie, the one pipe from the highest natural point of the system, doesnt matter if its got air in it as long as no air is left in the rest of the system, this pipe would lead to the top of the header tank. The pipe from the bottom of the tank to a low point in the system would always be full of water and is there to ensure that the system has as much water as it wants, as air flows out.

I cant see it being very easy to combine these two pipes. Is my thinking wrong?! Wouldnt be the first time. But if it is wrong, i would appreciate someone explaining why!

mike, do you mean the header tank or the bypass?!

[Edited on 19/8/05 by JoelP]

just to confirm, the heater bypass does currently run from the small outlet on the water pump to the entry on the carb manifold (might not be standard cos its on twin webers).

The expansion should be ok in between the top of the thermostat and any lower point, oui?! assuming two pipes is correct... probably just do it like that anyway

i was thinking plumb the expansion tank into the pipe from the water pump to carbs.

As long as you've got a presurised cap i can't see it being a problem.

I'll also have an 'air bleed' tube from the top of my radiator and themostat into the expansion tank. (ok, i might have to block off the radiator expansion once i've bled it due to space reasons).